, I came across a way to cleave English speakers: those that pronounce R’s (rhotic), and those that don’t(non-rhotic). From the wikipedia page on Rhotic and non-rhotic accents:

English pronunciation is divided into two main accent groups, the rhotic (pronounced /ˈroʊtɪk/) and non-rhotic, depending on when the sound typically represented in spelling with the letter R is pronounced. Rhotic speakers pronounce written /r/ in all positions, while non-rhotic speakers pronounce /r/ only if it is followed by a vowel sound (see “linking and intrusive R”), and not always even then.